Compressor and balancing device therefor



Feb. 11, 1936. w. E. JOHNgON 2,030,701

COMPRESSOR AND BALANCING DEVICE THEREFOR Fi'led Aug. 9, 195,5

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Wilf'r'id E. Johnson H15 Attov'neg.

Patented Feb. 11, 1936 UNITED STATES COMPRESSOR AND BALANCING DEVICETHEREFOR Wilfrid E. Johnson,

New York Schenectady, N. Y., assignor to General Electric Company,

a corporation of Application August 9, 1935, Serial No. 35,513

10 Claims. (Cl. 23o-58) My invention relates to compressors of thereciprocating type and balancing devices therefor.

It is frequently necessary to give special consideration to theelimination of unbalanced forces in compresssors of various types andespecially those used in refrigerating machines. These unbalanced forcesset up undesirable vibrations of the machine which are objectionable. Ingeneral, the forces to be considered in obtaining balance Ithas beenfound to be a comparatively simple matter to counterbalance the rotatingforces by the use of ordinary rotating eccentric balance weights.Greater difliculty has, however, been encountered in attempting toeliminate the unbalanced rectilinear forces and especially those set upby the reciprocating piston mechanism of the compressor.

It is an object of my invention to provide an arrangement for exactlybalancing the otherwise unbalanced reciprocatory rectilinear forces setup by the piston and associated mechanism of the compressor or the like.

Further objects and advantages of my invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to theaccompanying drawing in which Fig. l is a plan View, partly in section,of a Scotch yoke type two-cylinder refrigerant compressor provided witha balancing device embodying my invention; Fig. 2 is a side elevation,partly in section, of the compressor and balancing device shown in Fig.1; and Fig. 3 is an enlarged perspective View, partly in section, of aportion of the compressor and the balancing device therefor shown inFigs. 1 and 2.

Referring to the drawing, I have shown in Fig. 1 a two-cylinder Scotchyoke type refrigerant compressor including a cylindrical cross yoke IUand a pair of axially aligned oppositely acting cylindrical pistons IIand I2 which are rigidly secured to opposite sides of the cross yoke Iand arranged at right angles thereto. The pistons and I2 reciprocate incoaxial cylinder bores formed in cylinders I3 and I4, respectively,which are secured by bolts I6 to the top of the frame of an electricdriving motor I5. The compressor is driven by the rotating shaft I1 ofthe electric motor I through a crank I8, the upper end of which isjournaled in va cylindrical block I9 slidably fitted in the cross yokeI0. The lower side of the cross yoke I0 is provided with an elongatedslot 20 through which the crank I8 passes. Therotary motion of the crankI8 causes the pistons and I2 to reciprocate in the cylinders I3 and |4with a consequent reciprocation of the block I9 in the cross yoke I0 atright angles with respect to the axis of the pistons and I2.

The outer ends of the cylinders I3 and I4 are closed by rectangular mufeboxes 2| and 22, respectively, which are secured thereto by screws 23and 24. The mufe boxes 2| and 22 contain suitable valve mechanisms forthe compressor, and gaseous refrigerant is supplied to the interior ofthe cylinders I3 and I4 through intake conduits 25 and 26, respectively.The gaseous refrigerant compressed in the cylinders I3 and I4 by thepistons I land I2 is discharged therefrom through suitable valves andexhaust conduits 21 and 28, respectively.

'I'he unbalanced rotating forces set up by the eccentrically locatedcrank pin I8 and slide block I9 are balanced by suitable rotatingeccentric counterbalance weights, one of which is shown at 29 and whichis segmental in shape. 'Ihe couples set up between the balance weight 29and the crank pin I8 and the slide block I9 are balanced by the secondbalance weight secured to the lower portion of the shaft I 'I (notshown), the lower weight being positioned 180 about the shaft from theupper Weight 29.

A plurality of inertia members are provided for exactly balancing therectilinear forces set up by the reciprocatory motion of the pistons I Iand I2 and the driving mechanism therefor. In the illustrative form ofmy invention, a pair of duplicate segmental balance weights 30 and 3|are utilized as the inertia members. The balance weights 30 and 3| arepivotally mounted for oscillatory movement through arcs of less than 180in a horizontal plane at right angles to the axis of the motor shaft I1on stationary pivot pins 32 and 33, respectively, Which pass through thecentrally located bores in the hubs 34 and 35 of the balance weights 30and 3|. 'Ihe balance weights 30 and 3| are symmetrically positioned onopposite sides of the axis of the pistons I I and I2. It will be notedthat the balance Weights 30 and 3| are symmetrical about a verticalplane of symmetry bisecting the angle of the segmental upper surfacesthereof. This plane of symmetry is also the vertical plane of symmetryof inwardly extending links 36 and 31. The lower ends of the pins 32 and33 are rigidly supported, preferably on the top of the end shield of theelectric motor I5. The balance weights 30 and 3| are so connected to thepistons ,that the balance weights Vof the pistons and that the rate ofacceleration in such direction is exactly proportional to the rate ofacceleration of the pistons. It is of prime importance that the rates ofacceleration of the pistons and balancing mechanism should be' opposedand exactly proportional in order that the forcesY set up by each shallat all times be equal and opposite. In the illustrative form of myinvention, the balance weights 30 and 3l are provided with the inwardlyextending links 36 and31 which are integral with the inner sides of thehubs 34 and 35, respectively. The inner ends of the links 36 and 31 areprovided with cylindrical guide blocks 38 and 39. Square holes 4Iland 4|are broached or otherwise formed in the centers of the cylindrical guideblocks 38 and 39, respectively, and the inner ends of the links 36v and.31 extend within these holes. Pins V42 and 43 having their oppositeendsV journaled in holes 44and` 45 intheV guide blocks'38 and 39extendthrough'holes 46 and 41` in the inner ends of the links 3I` andv31, thus,pivotally connecting the'links and guide' blocks. The guideblocks 3,8 and' 39 are slidably supported in aV cylindrical 'crossguideV 48 which is welded, or otherwise rigidly'secured, tothe top ofthe cross yoke II] in axial alignment therewith as indicated at 49;Since the cross guide 48 in which the guide blocks 38 and-39frecprocateis rigidly secured to the cross yoke I0 of `the'piston mechanism,displacement of the inner ends of the links 36 and 31 axially of thepistons II andY I2 is prevented.

'I'he balance-weights 30 and 3| are designed to balance out all0 of theunbalanced reciprocatory forces set up by the entire piston'mechanismwhich'in the illustrativev form of my invention is vmade up ofthepistons I I and I2, the yoke I0 and the cross guide 48. Since the lengthof the links 36 and 31 between the pivots-at the-opposite ends thereofis 'iixed and since the distance between the centers of the pivots 32and 33 and the centers of the weights 30 and 3| is also lixed, thedisplacement ofV a point on the plane of symmetry of the weights 30 and3| along a component of motion parallel to the motion of the pistonmechanism will always be exactly proportional Yto the displacements ofthe piston mechanism. As av consequence, the acceleration of the weights30 and 3| in a direction parallel to the line of motion of the pistonmechanism will always be exactly proportional to the acceleration ofthepiston mechanism butin an opposite direction.

The oscillating balance weights 30 and 3| are so designed with respecttothe reciprocating piston mechanism that no unbalanced couples aboutany horizontal axis will appear in the completed system. This result mayconveniently-bey accomplished by individually designing each of thebalance weights in such manner that the product of inertia of eachweight about an axis lying in a horizontal plane passing through the;center oi gravity of the piston mechanismVV and about a vertical axispassing through the center of the pivotalsupport of the balance weightare equal to zero, each of the axes lying in the vertical plane ofsymmetry of the balance weight. This relation of the products of inertiaof the balance weights Amay be expressed mathematically by the equation:Y

A G=2mxyV=0 Where G represents the product of inertia of the balanceweight, m is the mass of anV infinitesimal particle of the balanceweight, and :c andy are the position co-ordinates of the particle withrespect to a pair of co-ordinate planes. One of the co-ordinate planesis a horizontal plane passing through the center of gravity of thepiston mechanism andthe other is the vertical plane of symmetry of thebalance weight.

It should be noted that it is not necessary that the balance weights 30and 3| be arranged in 'such manner that their centers of gravity lieinthe same horizontal plane as the center of gravity of the pistonmechanism. In fact, such an arrangement may result in unbalanced couplestending to cause vibratory movement of the compressor. As pointed out,however, it is necessary that the product of inertia of each of thebalance weights about a vertical axis passing through the pivot supportof the balance weight and a horizontal axis lying in a plane passingthrough the center of gravity of the piston mechanism, the axes lying inthe vertical plane of symmetry of the balance weight, be equal to zero.Such an arrangement is particularly useful. in refrigerant compressorsof the type illustrated, since it may be necessary orV at leastdesirableto locate the balance weights 39 and 3|.above the plane of thepistons I I and I2 in order to'provide suitable 1 space for the cylinderand other compressor tally. `In order toA determine experimentally theexact weight distribution required, one of the balance weights completewith its link is mounted on a pivot passing through the hub thereof.` Aweight is then rigidly attached to the inner end of the link of thebalance weight, this attached Weight being exactly equal to one-half theweight of the piston mechanism. It will be understood that by the termpiston mechanism the pistons I I and |2`are included, as well as thecross yoke ID and the cross guide 48. The center of gravity ofV thisweight must be placed exactly below the center of the pivot pin holeformed in the inner end of the link and in the Yplane of the center ofgravity of the piston mechanism. The'balance weight is then rotated onits pivotal support and portions of the same may be removed from theperiphery of the main body ofthe weight or from the side of the flangeformed on 'thevupper Yedge thereof until a true dynamic balance isobtained. The other weight may then be similarly balanced. When theweights have been dynamically balanced in the manner described,theproductof inertia of each balance weight about a vertical axispassing through thepivotal support thereof right angles thereto. Sincethe components of,

and 3| at r1ght angles to the line of movement of the pistons Since thecomponents of the movement of the balance weights 30 and 3| parallel tothe line of movement of the piston mechanism are always in a directionopposite to the movement of the latter, and since the acceleration ofthe balance Weights parallel to the piston mechanism is alwaysproportional to the acceleration of the piston mechanism, the horizontalforces set up by the piston mechanism are always balanced by the balanceweights. As pointed .out above, the balanced couples about anyhorizontal axis will appear in the system. It will thus be seen that Ihave provided a balance arrangement ln which all of the rectilinearforces in the compressor are exactly balanced.

'I'he balancing arrangement which I have provided is particularlyadvantageous in connection with a two-cylinder compressor in that ittends to smooth out the torque curve of the crank shaft. In the case ofa two-cylinder compressor, such as the one illustrated, when thecompressor pistons are moved from the extreme position shown in Fig. 1to the opposite extreme position, the crank shaft turns through an arcof 180. During the rst part of this movement, the piston will be movingon its intake stroke while the piston 2 is just beginning itscompression stroke. As a consequence, a comparatively small torque isrequired to turn the crank shaft duringv the first 90 of the halfrevolution noted. During the second 90 of the half revolution, thepiston 2 exerts its maximum compressive force and a comparativelygreater torque is required. During the first 90 of this movement,however, the inertia of the balance Weights 30 and 3| oppose themovement of the crank shaft, while during the second 90 of such movementthe inertia of the balance weights, which are also moving through thesecond portion of their arc of movement, aids the movement of the crankshaft. As a consequence, even though the motion of the balance Weight isof the same frequency as the pistons, double frequency torque is appliedto the crank shaft which is opposite in phase `to what is in eiect adouble frequency torque caused by the compression in the cylinders. Thetorque curve of the crank shaft is thus smoothed out appreciably.

While I have shown a particular embodiment of my invention in connectionwith a Scotch yoke type refrigerating machine compressor, I do notdesire my invention to be limited to the particular construction shownand described and I intend, in the appended claims, to cover allmodications Within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A reciprocating type compressor and balancing device thereforcomprising a reciprocatable piston, a plurality of inertia members,means including a plurality of pivots stationary with retion of saidcomponent exactly proportional to the rate of acceleration of saidpiston.

2. A reciprocating type compressor and balancopposite sides of the axisof said pistons and symmetrically with respect to said axis foroscillatory movement in an arc of less than 180, and means includinglinks connecting said inertia members and said pistons for oscillatingsaid inertia members about said stationary pivots and for acceleratingsaid inertia members in such oscillatory movement With a component ofmovement in a direction opposite to the direction of movement of andsymmetrically oscillatory movement in an arc of less than 180 linksrigidly connected to each of said inertia members and extendingtherefrom toward the placement of the inner ends of said links axiallyof said piston, the inner ends of said links being free to move at rightangles with respect to the axis of said piston.

4. A reciprocating type compressor and balancing device thereforcomprising a reciprocatable with respect to said axis of said piston.

5. A reciprocating type compressor and balancing device thereforcomprising a reciprocatable piston,'a pair of inertia members, means forpivotally supporting said inertia members on opposite sides of the axisof said piston and symmetrically with respect to said axis foroscillatory movement in an arc of less than 180, links rigidly connectedto each of said inertia members and extending therefrom toward the axisof said piston, guide blocks pivotally connected to each of said links,and means including a cross guide rigidly carried by said piston andpositioned at right angles to the axis thereof and adapted toy receivesaid guide blocks for preventing displacement of said guide blocksaxially of said piston,

with respect to said axis for said guide blocks being free to movein'said cross Y Y inertia members on opposite sides of the axis of saidpiston and symmetrically with respect to said axis for oscillatoryconnected to each of .said inertia members and extendinginwardlytherefrom toward the axis of said piston, guide blocks pivotallyconnected to each of said links, and means including a cross guiderigidly connected to said cross yoke in axial alignment therewith andadapted to receive said guide blocks for preventing displacement of saidguide blocks axially vof said piston, said guide blocks being free tomove in said cross guide at right Vangles to the axis of said piston.

'7. A reciprocating compressor of the Scotch yoke type and balancingdevice therefor comprising a cross yoke, Va pair of axially alignedpistons rigidly secured to said cross yoke on opposite sides thereof, apair of inertia members, means for pivotally supporting said inertiamembers on opposite sides of the axis of said pistons and symmetricallywith respect to said axis for oscillatory movement, links rigidlyconnected to each of said inertia members and extending inwardlytherefrom toward the axis of said pistons, guide blocks pivotallyconnected to each of said links, a cross guide integral with Ysaid crossyokeA in axial alignment therewith Vand adapted to receive said guideblocks for preventing displacement of said guide blocks axially of saidpistons, said guide blocks being free to move in said cross guide atright angles to the axis of said pistons.

8. A reciprocating type compressor and balancing device thereforcomprising a piston mechanism including a pair of oppositely actingpistons, a paid of inertia members having a vertical plane of symmetry,means including a plurality of pivots stationary with respect to thecompressor for pivotally supporting said inertia members on oppositesides of the axis of said pistons and symmetrically with respect to saidaxis for oscillatory movement in an arc of less than the product ofinertia of each of said inertia members about a pair of axes lying insaid plane of symmetry beingY equal to Zero, one oi' said axes beingvertical and passing through thecenter of said pivotal support of saidmember and the otherv of said axes lying in a horizontal plane andpassing through the center of gravity of said piston mechanism, andmeans including links connecting said inertia members and. said pistonsfor oscillating said inertia members about said stationary pivmovement,links rigidly axially aligned and aosofzoi ots and foraccelerating saidVinertia members in such oscillatory movement with a component ofmovement in a direction opposite to the, direction of movement of saidpistons and at arate of acceleration in the direction of Ysaid componentexactly proportional to thev rate of acceleration of said'pistons. i

9. A reciprocating type compressor and balancing device thereforcomprising a reciprocatable piston mechanism, a pair of inertia Vmembershaving a vertical plane of symmetry, meansl for pivotally supportingsaid inertia members on opposite sides of the axis of said pistonmechanism and symmetrical with respectV to .said axis for oscillatorymovement in an arc of less than 180,

the product of inertia of each of saidinertia.

members about a pair Yof axes lying in saidplane of symmetry being equalto zero, one of said axes being vertical and passing through the centerof said pivotal support of said member and the other of said axes lyingin a horizontal plane Vand passing'through the center of gravity of saidpiston mechanism,'links rigidly connected to each of said .inertiamembers andV extending therefrom toward the axis of said pistonmechanism, and means for preventing displacement of the inner endsofsaid linkszaxially of said piston mechanism, the inner ends of saidlinks being free to moveat right angles with respect to the axis of saidpiston mechanism.

10. A reciprocating compressor of the Scotch yoke type and Vbalancingdevice'therefor comprisinga piston mechanism including a cross yoke, apair of axially aligned pistons rigidly secured to said Vcross yoke-onopposite sides thereof, a cross guide integral with said cross yoke inaxial alignment therewith, said balancing device including a pair ofinertia members havingV a vertical plane of symmetry, means forpivotally supporting said inertia members'on opposite sides of the axisof said pistons and symmetrically with respect to saidaxis foroscillatory movement, a product of inertia or each of saidinertia/members about a pair of axes lying in said plane of symmetrybeing equal to zero, one of said axes being vertical and passing throughthe center of Y said pivotal support of said inertia member and theother of said axes lying in a horizontal plane and passing through thecenter .of gravity of said pistonmechanism, links rigidly connected toeach of said inertia members and extending inwardly therefrom toward theaxis of said pistons, guide blocks pivotally connected to each of saidlinks and Vslidaloly mounted in said cross guide, said guide blocksbeing free to move in said cross guide only at right angles to the axisVof said pistons.

' WILFRID E. JOHNSON.

